In carrying out a seismic exploration, a standard procedure is to drill holes into the geologic formations of interest and to plant explosive charges in the bore holes. The charges are then detonated and appropriate measurements recorded to enable evaluation of the formation.
There are a number of problems associated with this seismic drilling. One of these occurs during the actual blast. Unless the hole is properly plugged prior to detonation, a large proportion of the energy of the blast escapes upwardly through the hole and is thus not properly directed through the formation of interest.
There is therefore a continuing need for a bore hole plug which is simple and inexpensive in construction yet sufficiently durable to remain in place for extended periods and to withstand the force of the blast. To date, a variety of plugs have been proposed and used, but these do not satisfactorily meet all of the criteria set out above.
In addition, plugs are required to be inserted into bore holes to support concrete, earth or other topping materials used to close the hole. Accordingly, a simple plug which could withstand the force of the blast and remain in the hole as a topping plug would be highly desirable. Such a plug could be used as a topping plug only, if required.
The bore hole plug of the present invention is intended to alleviate the problems discussed.